The present invention, relates to hand-operated cutting tools.
The present invention, more particularly, relates to hand-operated tools for cutting insulation batts.
The present invention, most particularly, relates to hand-operated tools for cutting insulation batts, during the process of installing such insulation batts in a building wall, or between the rafters of a building.
U.S. Pat. No. 5,075,974, granted to Edward McIlhatten, on Dec. 31, 1991, discloses a cutting tool for use on insulation batts, or other fibrous compressible materials. The cutting tool comprises a utility knife housing, having a razor-type cutting blade, extending from one end thereof. The elongated housing is seated in a "U"-shaped cradle, that is attached to two parallel rods, or wires. Flexible straps extend around the cradle and the knife housing, to retain the knife housing in a fixed position on the cradle.
The parallel rods terminate in guide rings, near the end of the knife housing that carries the cutting blade. The parallel rods are reversely curved, to form a spring system, that includes wire-like posts, extending upwardly through the above-mentioned guide rings. The spring system can be positioned against a batt of insulation, to exert a compressing action on the fibrous batt material when a downward manual pressure is exerted on the knife housing. During downward motion of the knife housing, the guide rings slide down on the parallel posts, presumably for the purpose of ensuring a true vertical motion of the knife housing. After the insulation batt has been compressed, the knife housing can be drawn across the batt surface, so that the razor blade cuts through the compressed batt thickness.
The tool shown in U.S. Pat. No. 5,075,974, is believed to have some disadvantages. For example, the cost of manufacture is relatively high, because several component parts and assembly operations are required to form a complete assembly. The cradle has to be specially affixed to the parallel rods by bending edge areas of the cradle around the rod material. Several bending operations are required to form the wire, or rod, material into an operative spring shape. Also, the guide rings have to be specially formed, and the flexible straps have to be attached in some manner to the undersurface of the cradle. In light of the above, the overall cost of manufacture is believed to be relatively high.
Further, an operational disadvantage of the '974 patented system, is that the flexible straps are relatively close together, such that the knife housing is apt to wobble, or become loose, in the cradle, during operation. Also, the presence of the straps makes it somewhat difficult for the workman to get his hand around the knife housing. The straps and cradle add to the side-to-side bulk dimension of the tool, so that the workperson can not get a firm grip on the knife housing. Thus, the operator has to grip the straps, rather than the knife housing.
It is believed that the batt compressing action of the parallel rods, or wires, might also be less than satisfactory. Since the rods are spaced apart, they do not compress the batt, in the plane of the cutter blade. Instead, the rods, or wires, compress the batt in two parallel planes on either side of the cutter plane. Therefore, the cutter moves through batt material that is only partly compressed.
It is further believed that the wire-type posts may tend to bend, or buckle, since the associated guide rings move obliquely to the posts, during the downstroke of the knife housing. As the rings move down on the posts, the angulations of the rings on the posts change, so as to generate a twisting, or bending force on the posts.
Also, it is believed that the overall size of the tool assembly in the '974 patented arrangement, is excessive. As shown in FIG. 1 of the '974 patent, the overall length of the wire structure is appreciably greater than the length of the utility knife per se. A workman, working in close quarters, might find the '974 patented assembly too bulky for easy use. Additionally, it is believed that the wire construction is fragile and subject to bending of the wires. If the wires are bent out of parallelism, they will tend to spread apart when downward pressure is applied to the knife housing. In such an event, the guide rings would bind on the posts.